(a) Field of the Invention
The present invention relates to a toner for use in developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like, in particular relates to a toner for use in dry type electrophotography that has been incorporated with a specific lake pigment effective for controlling said toner to be at positive polarity.
(b) Description of the Prior Art
The toners for use in the dry type developer used for developing electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing and the like are generally comprised of binder resins such as styrene resin, phenol resin and the like; charge controlling agents; and coloring agents such as carbon black, Nigrosine and the like in case of necessity. As the charge controlling agents there are used, for instance, metal-containing dyes in the case of charging the toners negatively, whilst there are used (1) Nigrosine dyes, (2) certain kinds of basic dyes (Japanese Laid Open Patent Application No. 11455/1976), (3) certain kinds of lakes of xanthene dyes (Japanese published patent application No. 9906/1984) and the like in the case of charging the toners positively.
However, the latter controlling agents are defective in the efficiency of charging the toners positively, that is the controlling agent shown in the preceding (1) is defective in the marked unbalance in charging characteristics between manufacturing batches, the marked changes in course of time, and the like; the controlling agent shown in the preceding (2) is defective in that it is not fully dispersed in the binder resin used in the toner and further charging is unstable against changes in temperature and humidity; and the controlling agent shown in the preceding (3) is more stable against changes in temperature and humidity than that shown in the preceding (2) but is unstable in charging because it is not fully dispersed in the binder resin used in the toner. In the light of the aforegoing, further improvement has been called for.